It's definitely a good way to go. It's not the first time he's let someone kill him as a climax beyond climax (asphyxiation is a particularly exciting way to go) but it's nowhere near common enough to have lost its thrill. Besides, in this instance he's aware he's giving Spike more than just the high of having power over his life and death. He's giving him, literally, his life blood and that has to be an incredible high, even without the extra special zest of his particular blood. He's almost laughing with the high of it as he goes out, body sagging limp and heavy against Spike as the wound from Spike's teeth heals and disappears before Spike's very eyes.
And it's less than a minute before he's gasping back into life, taking his own weight back from Spike and laughing with exulation. "Oh fuck, that was hot!"